GROWTH OF BISMUTH GERMANATE [BI(4)GE(3)O(12), BGO] USING THE HEAT EXCHANGER METHOD (HEM)

A NOVEL MATERIAL, BISMUTH GERMANATE [BI(4)GE(3)O(12), BGO] SINGLE CRYSTAL IS A PRIMARY SCINTILLATOR WITH A RADIATION LENGTH OF 1.12(4)CM. BGO POSSESSES MANY ADVANTAGES OVER PREVIOUSLY USED SCINTILLATION CRYSTAL NAI(T1), SUCH AS, LARGE AVERAGE ATOMIC NUMBER, STRONG RESISTANCE AGAINST X-RAY, STABILITY OF CHEMICAL PROPERTIES, NON-HYROSCOPIC NATURE AND MUCH SMALLER AFTERGLOW. BGO SCINTILLATORS HAVE FOUND USE FOR XCT, POSITRON CT AND COMPACT Y CALORIMETRY. THE PROBLEM WITH BGO IS THAT IT IS NOT PRODUCED PRESENTLY IN LARGE VOLUME AND HIGH QUALITY. IT HAS BEEN ESTABLISHED THAT THE PURITY AND CRYSTAL DEFECTS STRONGLY INFLUENCE THE SIGNAL OUTPUT FROM BGO CRYSTALS. THE PRESENT PROPOSAL IS A FEASIBILITY STUDY OF BGO CRYSTAL GROWTH USING THE HEAT EXCHANGER METHOD (HEM). THIS PROCESS IS A SIMPLE DIRECTIONAL SOLIDIFICATION TECHNIQUE WHICH HAS PRODUCED LARGE CRYSTALS OF HIGH QUALITY AT LOW COST. THE INHERENT ADVANTAGES OF HEM WILL BE UTILIZED TO GROW HIGH PURITY BGO CRYSTALS WITH MINIMUM CRYSTAL DEFECTS. THE SHAPE OF THE SOLID-LIQUID INTERFACE DURING GROWTH IN HEM NECESSITATES GROWTH OF THE CRYSTAL OFF THE INTERFACE AND AWAY FROM THE CRUCIBLE. THIS FEATURE MAY BE IMPORTANT IN ALLOWING REUSE OF PLATINUM CRUCIBLES WHICH WILL RESULT IN SIGNIFICANT REDUCTION OF COSTS.